Hi Roberto, thank you for your question!
The BoldGrid Easy SEO plugin adds an additional form that appears after your page content when working in the Visual editor for a page or post.
The first tab in that form allows you to assign Keywords or a Keyword phrase to that Page or Post to tell search engine what your content relates to. This guide from our support center (https://www.boldgrid.com/support/boldgrid-easy-seo-plugin-product-guide/what-is-a-keyword/) goes over some of the SEO basics related to keywords and provides some suggestions on how to optimize the keywords for your content.
I hope this helps you get your keywords configured and please let us know if there is anything else that we can do to help.